In this study, we investigate how miscibility develops in naturally fractured reservoirs. We select and simulate compositionally a sector model of a real and highly naturally fractured reservoir of type 2, and the behavior of the reservoir under the influence of different gases injection, including methane, carbon dioxide, lean and rich gas investigated. The minimum miscibility pressure of each gas and the optimum gas injection rate is determined. The effect of injected gas type on solution gas–oil ratio, surface tension, and viscosity of reservoir fluid studied. Results of this study show that the oil recovery factor in the simulation sector model over 25 years of simulation for the natural depletion scenario is 15.2% while for the miscible gas injection at the optimum injection rate is 16.7, 18.8, 17.46, and 19.4% for methane, carbon dioxide, lean gas, and rich gas respectively. Also, an improvement in the development of miscibility in the case of rich gas injection at this type of natural fractured reservoirs observed. Article Highlights To reach the highest RF, Gas Injection rate optimization is necessary at this type of NFRs. Injection of methane and lean gas at higher rates causes faster gas breakthrough and leads to lower ultimately oil. The rich gas shows better miscibility condition than other gases at this type of NFRs.